In AP Music Theory, a consonant interval is one that sounds stable and at rest (unisons, 3rds, 5ths, 6ths, and octaves), requiring no resolution. Consonance is the baseline of common-practice harmony; dissonant notes are heard as embellishments that must resolve back to consonance.
Consonant describes intervals and harmonies that sound stable, settled, and "at rest." In the common-practice style the AP exam tests, the consonant intervals are the perfect unison, perfect octave, perfect fifth, and the major and minor thirds and sixths. The perfect fourth is the tricky one. It counts as consonant between upper voices but is treated as dissonant against the bass, which is why second-inversion (6/4) chords need special handling.
Think of consonance as harmonic home base. A consonant interval doesn't create tension, so it doesn't have to go anywhere. Everything else in tonal music is measured against it. Dissonant notes (seconds, sevenths, tritones, and most nonchord tones) create tension precisely because your ear expects them to resolve back to a consonance. So when you analyze a passing tone or a chordal seventh, you're really tracking a trip away from consonance and back again.
Consonance is the silent rulebook behind almost everything you do in AP Music Theory part writing and analysis. Eighteenth-century voice-leading procedures, the standard the FRQs hold you to, are built on the idea that voices move mostly in consonant intervals and that any dissonance is prepared and resolved. When you write a bass line against a given melody, you're choosing notes that form consonances (3rds, 6ths, 5ths, octaves) with the melody on strong beats. When you label embellishing tones, you're identifying the notes that break consonance and explaining how they resolve. If you can't instantly sort intervals into consonant and dissonant, both tasks fall apart.
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Visual cheatsheet
view galleryDissonant intervals
Consonance and dissonance are two sides of one system. Dissonant intervals (2nds, 7ths, the tritone) create the tension; consonant intervals release it. Tonal music is basically a controlled cycle of leaving and returning to consonance.
Embellishing Tones
Every nonchord tone, whether a passing tone, neighbor tone, escape tone, or anticipation, is defined by how it departs from and returns to consonant chord tones. The decoration only works because the consonant frame underneath stays intact.
Chordal Seventh Resolution
The seventh of a chord is a dissonance built into the harmony itself, and it still obeys the rule. It resolves down by step to a consonant chord tone in the next harmony, which is why V7 to I feels so satisfying.
Common Practice Era voice leading
The 'eighteenth-century procedures' the FRQs demand are largely rules about managing consonance. Avoid parallel fifths and octaves (too much bare perfect consonance moving together), favor 3rds and 6ths between voices, and resolve every dissonance.
You won't usually see a question that just asks "is this interval consonant?" Instead, consonance is the skill underneath the questions. The 2025 SAQ asked you to complete a bass line for a melody "following eighteenth-century voice-leading procedures," which means choosing bass notes that form proper consonances with the melody and avoiding parallel perfect intervals. Multiple-choice questions about embellishing tones, like distinguishing an escape tone from a neighbor tone, hinge on spotting which notes are dissonant against the harmony and how each one moves back to a consonant chord tone. So your job is to identify consonant versus dissonant intervals fast, then use that to write correct counterpoint and label nonchord tones accurately.
Consonant intervals (unisons, 3rds, 5ths, 6ths, octaves) sound stable and can sit still. Dissonant intervals (2nds, 7ths, tritones, and 4ths against the bass) sound tense and must resolve, usually by step, to a consonance. The confusion trap is the perfect fourth, which is consonant between upper voices but treated as a dissonance above the bass.
Consonant intervals in common-practice style are the perfect unison, octave, fifth, and the major and minor thirds and sixths.
The perfect fourth is consonant between upper voices but counts as a dissonance when it occurs above the bass.
Consonance needs no resolution; dissonance does, and that asymmetry drives all tonal voice leading.
Embellishing tones like passing tones, neighbor tones, and escape tones are dissonances that decorate a consonant framework and resolve back into it.
When you write a bass line on the FRQ, strong-beat notes should form consonances with the melody, and parallel fifths and octaves are off limits.
Thirds and sixths are called imperfect consonances and are the workhorse intervals of good two-voice counterpoint.
A consonant interval sounds stable and doesn't need to resolve. The consonant intervals are the perfect unison, perfect fifth, perfect octave, and major and minor thirds and sixths.
Both, depending on context. Between two upper voices it's treated as consonant, but against the bass it's treated as a dissonance, which is why 6/4 chords are restricted in common-practice writing.
No. Consonance is a technical category, not a taste judgment. It means the interval is stable and doesn't require resolution under common-practice rules, whether or not you personally find it pleasing.
Consonant intervals (3rds, 5ths, 6ths, octaves, unisons) are stable and can stay put. Dissonant intervals (2nds, 7ths, tritones) are tense and must resolve, typically by step, into a consonance.
Embellishing tones are dissonant notes added against a consonant harmonic framework. You identify each type (passing, neighbor, escape, anticipation) by how it leaves a consonant chord tone and how it resolves back to one.